Figure 1.

(a) Displaced harmonic oscillator model of molecular spectroscopy is characterized by vibrational frequency (ω₀), Huang–Rhys factor (), and electronic energy shift (ℏω_eg). (b) Measured vibrational quantum beat signals (top) can be Fourier transformed to produce femtosecond coherence spectra (FCS) for each mode (middle), which can then be classified as a fundamental, overtone, or combination-band mode and then fit using the appropriate model. (bottom) The fit yields the parameters and ω_eg, as well as the electronic dephasing (γ).